In conventional "wet" silver halide based color photographic processing systems, an imagewise exposed photographic element, for example color paper designed to provide color prints, is processed in a color developer solution. The developer reduces the exposed silver halide of the photographic element to metallic silver and the resulting oxidized developer reacts with incorporated dye-forming couplers to yield dye images corresponding to the imagewise exposure. As silver is generally gray and desaturates the pure colors of the dyes, it is desirable to remove it from the dye images. Silver is conventionally separated from the dye images by a process of bleaching the silver to a silver halide and removing the silver halide by using an aqueous solvent, a fixing bath. This fixing bath also removes the undeveloped original silver halide. Commonly, the bleach and fix are combined into one solution, a bleach-fix solution.
Bleach-fix solutions commonly contain iron, ammonium, ethylenediaminetetraacetic acid, thiosulfate and, after use, silver. These components of "wet" silver halide processing are the source of much of the pollution from photofinishing processes.
"Dry" silver halide based color photographic processing systems have been proposed which employ thermally developable color photographic material. Such thermally developable materials generally comprise a light sensitive layer containing silver halide, a photographic coupler or other dye-providing material, and a color developing agent as disclosed, e.g., in U.S. Pat. Nos. 4,584,267 and 4,948,698 and references cited therein. After image-wise exposure, these elements can be developed by uniformly heating the element to activate the developing agent incorporated therein, thereby eliminating the need for wet processing with a developer solution. In some thermally developable systems, the dye-providing materials are designed to form diffusible dyes upon heat development, which may be transferred to an image-receiving layer either during thermal development or thereafter in a separate step. Such thermally developable diffusion transfer color photography systems are disclosed in U.S. Pat. Nos. 4,584,267 and 4,948,698 referenced above. These systems also eliminate the need for bleach-fix steps with processing solutions and the resulting effluent wastes.
While dry processing systems as discussed above are beneficial in that they eliminate the need for processing solutions and the resulting waste, they require additional materials, such as developing agents, to be incorporated into the thermally developable photographic element itself. Also, the levels of silver halide necessary for heat developable systems are generally substantially higher than those required for conventional wet systems. The presence of such additional materials can detrimentally affect the cost, performance, and storage properties of such elements.
It would be desirable to provide a photographic processing system which would reduce the amount of waste processing solution effluents generated by the overall processing system while retaining the benefits of image quality and industry compatability which are derived from wet development with conventional developing solutions.